The broad, long-term objective of this study is to further our understanding of the endocrinology of the corpus luteum by investigating regulatory mechanisms at the genetic normal cellular growth processes in physiological systems. However, expression of proto-oncogenes has also been associated with uncontrolled growth, i.e. breast, ovarian, colon, bladder and stomach tumors in humans. Within the endocrine system, the mammalian role in cycle regulation and fertility control. Thus, it is an ideal organ, not only to study cellular proliferation in a normal tissue, but to study how the expression of proto-oncogenes is associated with the action of growth factors and hormones in regulating luteal function. The corpus luteum of the cow will be used to identify specific proto-oncogenes that are turned on and off during the genesis of the corpus luteum. Relative levels of expression will be correlated to luteal size, and progesterone concentrations in tissue and plasma. Proto-oncogene expression at the transcriptional level will be detected by dot-blot and Northern-blot hybridizations. Progesterone concentrations will be determined by RIA. Using these same analytical techniques, the regulation of proto-oncogene expression by luteinizing hormone and growth factors in the early corpus luteum will be studied in a long-term culture system. It is anticipated that these results will contribute new information in the reproductive physiology of the corpus luteum and gene expression, and will provide insight into the regulation of growth and development in normal tissue.